I certainly read doubts about the AF, especially off the center point.
However, the effusive praise, perhaps well deserved, won't light a fire under Sigma to address the AF problems.
The AF problems are isolated meaning some lenses are perfect some are junk. This is much better than all lenses being slightly off. I don't mind buying multiple copies from multiple retailers (to ensure they come from different batches) and connecting them with multiple bodies if it means I will get a perfect setup.
I bet the dealers mind your deliberately wasting their time and money.
5D IV, 5DS R, 7D II, EOS-M, Powershot G3 X, 400mm DO II, 300/2.8 II, 1.4xTC III, 2xTC III, EF 1.8 STM, EF 70-200/4 IS, EF 24-105, 15-85, 100-400 II, Sigma 10-20, Sigma 150-600mm C, EOS-M5 15-45, f/2 22, 11-22, Samyang 8mm f/2.8 fisheye